It is well-known from the related art to grow a semiconductor layer over a semiconductor substrate in a pillar shape with a narrow diameter and a height which is sufficiently long compared the diameter. A structure in which the diameter is narrowed to few tens of nanometers is known as a semiconductor nanowire or simply a nanowire. Formation of a pn junction or the like in the semiconductor nanowire to obtain a light-emitting element is also being researched.
For example, Patent Literature 1 discloses that a pn junction is formed in a long axis direction, which is a growth direction, of the semiconductor nanowire to form a light-emitting element. Patent Literature 2 and Patent Literature 3 disclose methods of manufacturing a light-emitting element having a quantum well structure in the nanowire. Patent Literature 4 and Patent Literature 5 disclose a light-emitting element having a pin junction in a growth direction of the nanowire. Patent Literature 6 discloses a method of manufacturing a light-emitting array having a red light-emitting element, a green light-emitting element, and a blue light-emitting element by simultaneously forming a plurality of semiconductor nanowires having different compositions and different band gaps from each other over one substrate.
As a technique related to the present invention, Patent Literature 7 discloses a thin film semiconductor element in which, for an amorphous silicon film provided over a substrate, after a natural oxide film is removed, the structure is immersed in a H2O2 solution for a short period of time to newly form an oxide film of a very thin thickness, and a laser annealing process is applied through the oxide film to crystallize the film. With such a configuration, the crystal grain size can be set to about 200 nm to about 300 nm, and a percentage of the (111)-orientation can be significantly improved. Here, in an X-ray diffraction measurement, {(111) diffraction intensity/(220) diffraction intensity}=(111)-orientation percentage. Patent Literature 7 discloses that, while the (111)-orientation percentage is about 1.8 when the crystals of polycrystalline silicon are completely randomly oriented, the (111)-orientation percentage can be improved to 60 with the above-described process.